The present invention relates to an apparatus for molding foam articles such as foam cushions for automotive seats and in particular to an apparatus having improved means for sealing the mold lid to the mold bowl to reduce the occurrence of foam leakage from the mold.
Large foam articles such as the foam pads in automotive seats are typically formed in large molds having a lower portion called a bowl and an upper portion called a lid. The bowl and lid when closed together define a mold cavity or cavities in which foam articles are molded. The molding process is accomplished by filling the bowl with a predetermined quantity of a liquid foaming agent. The lid is then closed upon the bowl and the liquid agent reacts, over a period of time, generating gases to produce air bubbles and expands to fill the mold cavity with foam. If the lid is not properly sealed against the bowl, foam can leak from the mold cavity, between the lid and bowl, forming what is known as mold flash extending from the molded article. This mold flash is removed from the molded article by a time consuming manual cutting process.
Accordingly, it is an object of the present invention to provide an improved mold for foam articles which reduces or eliminates the foam leakage which produces mold flash.
The apparatus of the present invention forms both the bowl and the lid with inclined sealing surfaces about the perimeter of the mold cavity. The sealing surfaces are inclined generally downwardly and inwardly toward the mold cavity and form the only contact between the bowl and the lid. The lid is mounted to a carrier frame which moves the lid between open and closed positions. The lid is movably attached to the frame so as to "float" on the frame. As the inclined sealing surface of the lid contacts the inclined sealing surface of the bowl, the lid is enabled to self align upon the bowl. The carrier frame is then latched to a base frame upon which the bowl is supported. This secures the carrier frame and lower frame in position relative to one another. The bowl in turn is supported upon the base frame by a resilient support, such as an air cushion.
The upper frame carries a plurality of adjusting bolts which are threaded to the upper frame and are adjusted to bear against the upper surface of the lid. These bolts are spaced from one another and are generally located about the periphery of the mold cavity. These bolts apply pressure to the lid, preventing the lid from bending or otherwise distorting which can result in a leak between the lid and bowl.
The air cushion beneath the bowl allows the bowl to float under the pressure applied by the lid and to seek an even pressure distribution about the periphery of the mold cavity along the sealing surfaces. The result is a consistent sealing of the lid to the bowl, reducing the occurrence of leakage and mold flash. The air pressure in the cushion can be increased after the lid is latched in place to increase the pressure at the lid and bowl sealing surfaces.
Previous molds contained a fabricated steel frame between the carrier frame and the aluminum lid. The steel frame was used to attach the lid to the carrier frame. Likewise, the bowl included a fabricated steel frame for mounting the bowl on the base frame. With the mold of the present invention, all of the mounting features for the lid and bowl are cast directly into the lid and bowl, eliminating the need for the fabricated steel frames. This reduces the complexity and cost of the mold. The adjusting bolts mentioned above have previously been used between the carrier frame and the fabricated steel frame of the lid. Since the adjusting bolts on the carrier frame now bear directly against the lid, the force from these bolts is transferred to the sealing surfaces of the mold halves. With the prior use of a steel framework, the forces applied by these adjusting screws did not always translate into pressure at the mold sealing surfaces. However, the mold lid is in need of reinforcement with the adjusting screws acting directly on the lid. Gussets have been added to the lid for this purpose.
To improve the molding operation, the bowl and the lid are both equipped with fluid passages for circulating heated water or other liquid through the mold halves to maintain a predetermined mold temperature.
Further objects, features and advantages of the invention will become apparent from a consideration of the following description and the appended claims when taken in connection with the accompanying drawings.